Lewis County,

116o24’55” 46o28’01” Accreted KJim Island Arc Tcr KJim Jacks Creek Fault 116o42’45” 46o19’32” 95 Reubens Tcr Tcr 12

Winchesterinchester Craigmont 64 Kamiah Tcr TR mh Craigmont Nezperce 46o13’33” Fault 95 o 84 KJim 116 00’43” Morrow Fault 162 Morrow Fault Tcr Tcr

KJim KJim

45o51’20” 116o47’20”

0 5 10 miles

0 8 16 kilometers

Digital Atlas of Idaho, Nov. 2002 http://imnh.isu.edu/digitalatlas Compiled by Reed Lewis, Idaho Geological Survey http://www.idahogeology.org Lewis County Lewis County, on the south side of the , contains the steep sided Camas Prairie plateau underlain by Miocene lava flows of the Columbia River basalts. Poking through at several places are Cretaceous and Jurassic island arc rocks of the Accreted terranes. The Suture zone runs just east of the county line along the Clearwater River through Kamiah. These plateaus are unusual, since the flat ground is on top, and the cities are generally in narrow valley bottoms. The Clearwater River cuts through the plateau, following the track of the Cretaceous suture zone. Written by P.K. Link, 9/02

Description of Units for Lewis County, Idaho

Tcr Miocene basalt (Columbia River Basalt Group); flood basalt, extensively exposed in western Idaho; fed by fissures, many of which are near the Idaho- border. Flowed eastward up valleys cut into the Idaho mountains. KJim Dioritic and gabbroic rocks of the Blue Mountains island arc terrane. Some are about 140 Ma.

TR mh Martin Bridge and Hurwal Formations (Wallowa Terrane).

Symbols

Geologic unit contacts with unit Overturned anticline: trace of axial Yp designation. plane.

Normal fault: certain; dashed where Overturnedsyncline: trace of axial approximately located; dotted where plane. concealed. Location of ISU Rockwalk rock Thrust fault: certain; dashed where from each county. approximately located; dotted where concealed. Cities Detachment fault: certain; dashed Feature location where approximately located; dotted where concealed. Roads Anticline: trace of axial plane: large Interstate Route arrow indicates direction of plunge. 15 U.S. Route Syncline: trace of axial plane: large 95 arrow indicates direction of plunge. 1 State route